As the stock market staged a modest rally today despite scary economic data, investors let a little air out of the high-flying price of long-dated U.S. Treasuries, slowing what had turned into a parabolic rise in government-bond prices.

Adding to the bearish action this afternoon was a report from Morgan Stanley analyst Arnaud Mares saying just about the most exciting thing anyone can ever say about government bonds, especially when so many people have been lending countries money as fast as they could: They are not going to pay you back!

“Governments will impose a loss on some of their stakeholders,” Mares wrote. “The question is not whether they will renege on their promises, but rather upon which of their promises they will renege, and what form this default will take.” The sovereign-debt crisis is global “and it is not over,” he wrote.

Sneaky deadbeat nations! Mares said that countries probably won’t fall behind on their payments outright, but are more likely to inflate their currencies, paying bonholders back with money that’s worth far less than the money they borrowed.

He compared borrowing nations to people who took out huge loans at the peak of the housing bubble, and bondholders to the banks that did the lending. If Mares is right, it’s we’re in for another spectacular display of wealth destruction as bond buyers pile out of that market like buffoons out of a clown car.